Hypoallergenic formulas or compositions, which are also referred to as elemental formulas, are characterized in that they contain protein hydrolysates such as soy protein hydrolysate, casein hydrolysate, whey protein hydrolysate or a combination of animal and vegetable protein hydrolysates as a major source of nitrogen. The protein hydrolysates comprise short peptide fragments and/or free amino acids instead of the intact protein found, for example, in cow's milk and soy protein isolate-based formulas. These short peptide fragments and free amino acids have been found to be less immunogenic or allergenic than intact proteins.
In addition to protein hydrolysates, most nutritionally balanced hypoallergenic formulas contain carbohydrates, lipids, vitamins, minerals and are supplemented with additional amino acids to upgrade the nutritional quality of such formulas. These hypoallergenic formulas are utilized for feeding infants, children and adults who have allergies or sensitivities to intact protein, and are often medically used in the treatment of cystic fibrosis, chronic diarrhea, galactosemia, small bowel resection, steatorrhae and protein-calorie malnutrition.
One well known problem in the preparation of hypoallergenic formulas is that extensive protein hydrolysis by acids or enzymes is necessary to provide the short peptides and amino acids utilized in the formulas to render such formulas hypoimmunogenic. These extensively digested and hypoimmunogenic protein hydrolysates have the undesirable characteristic of loss of capacity to emulsify fat and form physically stable emulsions that do not separate during storage.
Another common problem encountered in the preparation of hypoallergenic formulas is the formation of undesirable brown color as a result of the reaction between the carbonyl groups of reducing sugars and the nitrogen-amine-containing compounds such as amino acids in the formula (Maillard type reaction), especially at elevated temperatures encountered during sterilization. In addition to the brown color formation, Maillard type reaction also results in loss of the nutritional value of the protein hydrolysate.
U.S. Pat. No. 4,414,238 shows an elemental diet composition comprising carbohydrates, amino acids and/or low molecular weight peptides and lipids. The elemental diet of that patent has a lipid component in the form of an emulsion consisting of lipids, an emulifier selected from the group consisting of mono- and diglycerides, and a corn starch modified with succinic anhydride and is stable and non-browning at a low pH of about 3 to 4.4.
The present invention provides an improved hypoallergenic formula which does not require emulsifiers such as mono- or diglycerides, does not form a brown color at a higher pH range than previous hypoallergenic formulas, and is a stable emulsion. Furthermore, the hypoallergenic formula of the present invention enables suspension of the insoluble calcium and phosphorus salts which are commonly contained in such formulas.